The individual observations forming the background for the invention emanate from large-scale animal experiments on mice, however in which solely human drugs (cytostatics) were used which all are already familiar and applied in clinical practice in the USA. A cytostatic usually denotes a drug that affects the proliferating capacity of the cells by its inhibitory action of DNA, RNA or protein biosynthesis in general; sometimes these drugs are called antiproliferative or cytostatic agents, or mitotic poisons.
It is recognized that malignant diseases form an important category among diseases in general, being without adequate therapy in particular. All presently used cytostatics are, firstly nonspecific, and secondly, toxic. Although all medically active agents possess toxic properties, the applicable dosage range between the therapeutic dose and the toxic dose of the cytostatic is extremely narrow and the margin of error slight. Furthermore, administration of a cytostatic to the host may have profound effects on host defences, altering the delicate balance which may exist between host and tumor. As a consequence, suppression of host defences may not only facilitate cancerous progression, but may render the host more susceptible to infectious complications by pathogenic micro-organisms.
The desired result of chemotherapy of cancer is death of the cancerous cells, with destruction of the latter and sparing of viability and functions of the normal cells. These drugs, when administered to the tumor-bearer, simultaneously inhibit biochemical sites that are not unique to cancerous cells. Hence, the present cytostatics simultaneously kill or injure severely normal cells as well.
Most fateful for the design of the present-day anticancer drugs has been the generally accepted hypothesis according to which it should be granted that normal cells and cancerous cells have the same biosynthetic and regulatory mechanisms, and that cancer cells respond to a given anticancer agent in the same manner as do the normal homologous cells. In other words, if proliferating normal cells are injured by a noxious agent, it is postulated that the same holds true of cancerous cells.
In the following are given some of the experimental observations on mice which form the fundament for the invention. It appeared surprisingly that when separate observations, seemingly independent, were arranged in a purposeful order in relation to each other, the resulting constellation showed a new specific pathway for design of a rational anticancer therapy. These observations are in short:
(1) One of the most decisive prerequisites in general has been the use of mouse strains with known inborn (congenital) neoplastic potentialities, i.e., the ability to develop tumors. For the studies on which the present invention is based, results from experiments with female mice of the skin-tumor-resistant RA strain were used.(Sette,uml/a/ la, K (Editor) "Visualization of dormant cellular features in mouse epidermia correlated with skin tumor evolution." Acta Path Microbiol Scand Suppl 155 (1961)). Setala, Kai "Defective cell maturation, an alternative to accelerated cell division as target for cancer therapy", Progress in Experimental Tumor Research, Vol 5, p. 1 (1964).
(2) For the detection of delicate events or patterns in cell differentiation, keratinization of the epidermal cells was used as exponent for differentiation.
(3) The benign epidermal condition--generally called the stage of tumor promotion in experimental cancer research provoked by the known tumor promoter Tween 60.RTM. (polyoxyethylene sorbitan monostearate) and the malignant counterpart provoked by the carcinogen 9,10-dimethyl-1,2-benzanthracene (DMBA) are in all respects opposite to each other (Setala, Kai "Relation of benign and malignant epidermal hyperplasia in mouse", Proc. I Int. Conf. Univ. Perugia p. 529 (1962). Large-scale experiments have been performed. Parallel studies comprised tumor-production series, light, polarization and electron microscopy, histochemical and histoquantitative examination, and in vitro analyses on various mixed lipo/protein surface films. The total animal material now comprises about 30,000 mice with varying degrees of inherited susceptibility towards skin-tumor formation. In samples taken from 1,800 mice, 930,000 karyokinetic assemblies and 14,522,600 corresponding nucleated nondividing cells from various conditions of the epidermis were analyzed.
(4) It has been convenient to use relative high doses (nearby maximal doses allowed) of cytostatics for evaluation of their effects upon the target. However, to be able to detect delicate patterns in the target tissue, the dose of the cytostatic has to be as low and nondestructive as possible to avoid the disturbing development of mass injury, which would otherwise have masked subtle differences in the modes of response. This has been the guideline. For final evaluation, doses of cytostatics were selected which do not cause at all, or only in an infinitesimal degree, changes in the malignant (cancerous) condition, but in contrast cause strong effects in the normal target emanating from the same tissue of origin. (Setala, Kai "Differences in pharmacodynamic response to colchicine between benign and malignant epidermal hyperplasia" Acta Radiol. Suppl 237 (1965)). (Setala, K "Kontrare pharmakodynamische Antwortsweise der gutartigen und kanzerosen Epidermishyperplasie der RA Mause auf das onkolytische Alkaloid Vinca rosae Linn. "Naturwissenschaften Vol 52, p. 564 (1965).
(5) To reveal the degree and mode of effect of a given cytostatic, experiments were needed utilizing side-by-side three different targets: the benign (hyperplastic) condition, the malignant (cancerous) condition, and the normal tissue of origin, the epidermis.
(6) The results on which the new anticancer strategy and the composition of the invention are based were obtained in experiments in which 8 different known cytostatic agents were separately utilized. These were: the archetype mitotic poison, colchicine; vinblastine sulfate; phlorizin; triethylene thiophosphamide; sodium chloride of cyclophosphamide; humic acid (polymetic component of soil humus); fluorouracil; and SP-J-Sandoz.
(7) the results from experiments performed with the drugs given above show--among other things--that the normal epidermis and the benign (hyperplastic) epidermal condition are extremely susceptible to the effects of the subtreshold doses of the 8 cytostatics tested. Thus, even a dose of 60 gamma per day of the drug, given only once, provoked a vigorous response: a high number of pathological mitotic figures, and of epidermal "monster cells". The type of the karyokinetic injury was that characterized as pre-prophase-poisoning syndrome. In contrast, the malignant (cancerous) condition was extremely nonresponsive, almost indolent to the same cytostatic under related experimental circumstances. In addition, the karyokinetic disturbance did not reveal any pre-prophase-poisoning type otherwise characteristic of cytostatics in general. All 8 cytostatics tested revealed related results. Because at that time it was not possible to evaluate the final character of the nonresponsiveness of the malignant cells, the property was called "cytoplasmic barrier" of the malignant cells towards the effects of cytostatics.
(8) The results further revealed that the karyokinetic activity in the malignant (carcinogen-provoked) epidermal condition is significantly lower than that in the benign (hyperplastic, tumor promoter-provoked) epidermal condition. It was furthermore shown that the characteristic of the cancerous epidermal cells is thus not an intense cell proliferation rate, but in contrast a delayed and misguided cell differentiation (maturation) (Setala, K et al. "Verlangerte Lebensdauer der Tochterzellen bzw. herabgesetzte Mitoserate der Basalzellen als Ausdruck des Carcinogeneffektes in Mauseepidermis". Naturwissenschaften Vol 48, p. 673 (1961)).
(9) Following the observations made above under (7) and (8), it was recommended that the delayed and misguided cell differentation (maturation) should be used as a target for the design of a specific anticancer strategy, and not solely principles which should interfere with the karyokinetic activity only.
(10) Experimental result showed clearly that it is in fact possible to lower the degree of malignancy of the cancerous epidermal cells by forcing them to proceed towards re-differentiation. These observation further indicate that it is possible to arrest the malignant progression--at an experimental level--even by several different and fairly simple methods. Among these therapeutic attempts was utilization of adenosene triphosphate ATP, together with the tumor promoting substance Tween 60.RTM. (with its two-phase properties) while ATP served as the energy source (Setala, Kai et al., "Input of energy compelling carcinogen injured epidermal cells in mice to proceed with differentiation" Naturwissenschaften vol 48 p. 225 (1961)).
Further, the steroid cholesterol was beneficially utilized because of its role at and effects on the cell surface membrane (Setala, Kai et al. "Inhibitory action of cholesterol addition to Tween 60.RTM. on the tumor promoting and epidermal hyperplasia causing effects in mouse skin" Naturwissenschaften vol 46, p. 331 (1959)). This observation was later applied by other investigators. Furthermore, Tween 60.RTM. was used because of its hydrating (two-phase) and membrane-active properties, and urea in Tween 60.RTM. (Setala, Kai et al. "Inhibition of evolution of multiple skin tumours in mice. A simple technique based on cause and effect relationships", Multiple Primary Malignant Tumours (L. Severi, ed.) Perugia (1973) p. 393) because of its known alfa-helix-rupturing properties which increase the availability of "free" water molecules in the cells.
(11) However, a feature of cardinal importance is the intracytoplasmic 3-dimensional cytoskeleton composed of molecular chains - the cytodifferentiation organelle (in epidermal cells, keratinization organelle) detected by us 20 years ago. It is particular organelle that should be the target for anticancer attacks. Further, the existence of and changes in this organelle for the first time allows a direct insight into the mechanism underlying (experimental) skin carcinogenesis in mice.
Examination of sections cut serially at right angles to each other showed that the cells contain an intracytoplasmic 3-dimensional basket-like cytoskeleton. This is partly arranged around the nucleus, which the most peripheral parts of it are closely connected with paramembraneous structures and, partly, with the corresponding patterns of the adjacent cells. Cytodifferentiation occurs within this organelle. In the malignant cells, the organelle is deranged, rigid and--partly--increased in mass, while the cancerous cells are dehydrated. The presence of this differentiation organelle was first detected in epidermal cells (cf references on page 3, lines 1 to 7 and Setala, K et al., "Input of energy compelling carcinogen injured epidermal cells in mice to proceed with differentiation" Naturwissenschaften vol 48 p. 225 (1961)). Setala, K et al., "Mechanism of experimental tumorigenesis. 9. Sulphydryl groups, disulphide bonds, and birefringence in mouse epidermis after exposure to dipole-type tumor promoter and carcinogen" Acta Path. Microbiol. Scand. Vol 54, p. 39 (1962)). Thereafter the existence of the organelle has been confirmed and shown to exist in all eukaryotic mammalian cells.
(12) It has been shown that--under experimental circumstances--the carcinogen and the cytostatic act largely on the same target: both cause severe alterations in the 3-dimensional cytoskeleton. Hence, therapeutic exposures of the cancerous cells to a cytostatic means that the drug focuses its effects on a target already hardened by exposure to a carcinogen. This observation may explain the reason why the carcinogen-provoked malignant epidermal cells possess the "cytoplasmic barrier" against the effect of after-treatment with a cytostatic.
(13) It has suddenly and surprisingly now became evident that dimethylsulfoxide, DMSO, focuses its effects just towards the intracytoplasmic 3-dimensional cytoskeleton. In normal cells and in benign (hyperplastic) cells the cytoskeleton remains unchanged after exposure of the cell to DMSO (the same is true as to Tween 60.RTM.). In contrast the cytoskeleton of malignant (cancerous) cells becomes stabilized (dispersed) by the effect of DMSO exposure.
(14) the peculiar properties of DMSO may explain the reason why the cytoskeleton (composed of protein belonging to the actin-myosin-/actomyosin/-epidermin-fibrinogen group) of the malignant cells can so easily be stabilized. According to the literature on DMSO, this polar substance (the first hydrating substance utilized, Tween 60.RTM. is nonpolar-polar in nature) as a molecule behaves like a zwitterion having an electrostatic charge density on its oxygen atom comparable to that of the fluoride ion. Further, the DMSO anion interacts with water to form an A-region having two water molecules, i.e. a DMSO. 2H.sub.2 O complex. Additional studies on various biopolymers show that DMSO. 2H.sub.2 O complex helps to stabilize the helix structure of its target(s). DMSO is said to exist as a resonance hybrid having strong protein dispersing power. In other words, DMSO alters the configuration and water-binding capacity of proteins and other vital biopolymers, increasing their flexibility and looseness.
(15) As stated under (7) above, when the normal epidermis and the benign (hyperplastic) epidermal condition and the malignant (carcinogen-provoked) condition were topically exposed to the effects of the 8 cytostatics studied (only one cytostatic in each series), the normal cells and the cells of the benign hyperplasia responded extremely vigorously although the dose of the cytostatic was of a subthreshold order only. A high incidence of pathological cell division figures developed; further a high incidence of epidermal "monster cells" occurred. The volume of the cytoplasm increased mani-fold (up to 20-fold). The intracytoplasmic 3-dimensional cytoskeleton became unmasked. The cystatic-dependent alterations were evident already after 24 hours after a single exposure. In these two targets the changes were reversible and showed after 72 h a distinct tendency to recover. Addition of DMSO to the cytostatic-solution does not essentially alter the mode and degree of response.
In contrast, the mode and strength of the response of the malignant condition differed fundamentally from the above. Thus, in series without DMSO addition, the response was very weak or at places non-existent, only a very low incidence of epidermal "monster cells" developed. The intracellular vacuolization was of low degree, the size of the malignant cells did not essentially increase. The 3-dimensional cytoskeleton was only slightly altered. But, when the same cytostatic was administered in the presence of DMSO, the situation changed in a highly significant manner. Now the reaction was extremely vigorous and resembled in principle that seen in normal cells and the cells of benign (hyperplastic) condition. A high number of pathological mitotic figures developed, similarly now even epidermal "monster cells" occurred. Statistical analyses based on histoquantitative examination revelated that the differences between related parameter-pairs were highly significant (p &lt;0.001) in all series. Light, polarization and electron microscopy strengthened the statistical observations. The cytostatic-DMSO-provoked changes in the malignant (cancerous) condition were irreversible.